For those of you that don't want to click that link, i'll paste the other post here along with the reply.

QUESTION:

I am in the Boy Scouts and am starting on a new badge. I was browsing through random things to build on the internet and ran across http://wheely.cat.org.au/ and decided I was going to do the same but try to fit in a much smaller space, my backpack. So I started my search to build my own amp to power this system I was about to build and came across http://tangentsoft.net/audio/cmoy-tutorial/. It is a good idea to get started with but I started reading and it looks like it is just for headphones and I want something much louder and powerful enough to power a 12" subwoofer. Hopefully someone here could help me out a bit with this problem.

REPLY:

The power-amp equivalent of the CMoy is called a chip-amp. There are a number of different kinds: Gainclones, Tripath chip-amps, etc. diyaudio.com is the best place to take this up.

More powerfull means it needs more power i.e. in the way of batteries or mains... which is where high powered portable dreams fall flat. Also the more powerfull it gets, the bigger heatsink is needed.

Makeing a mistake during construction will most likely destroy your components, which is why just building a C-moy is good enough as a first project. One I think you can get your badge for just fine...

If you want a balance between a headphone amp and one that takes a garbage can look for a Class D chip amp that will run from about 12V. Then you can make 12V from batteries, either lots of single batteries like AA, C or D, or two of those large 6V batteries (can't remember size) or a battery from a UPS or any other 12V type. The issue becomes weight and size of hauling the whole thing around.

Class D chip amps don't sound great but they are not bad and they are typically very easy to work with. Can run 10W or so depending on configuration, load impedance, and voltage supply. 10W is actually not a bad amount of power.

For something even smaller look for National's Boomer amps and run it from 4xAA NiMH batteries (4.8V). 1-2W can put out some loud sound from a half-way decent speaker.